Thermoplastic particles which comprise an antiviral or antimicrobial agent

ABSTRACT

This invention relates to novel porous materials that possess antiviral and/or antimicrobial properties. The invention encompasses a porous material having antiviral or antimicrobial properties-which is comprised of a porous substrate and an antiviral or antimicrobial agent. The invention also encompasses a process for making porous materials that possess antiviral and/or antimicrobial properties and the products of the process.

1. FIELD OF THE INVENTION

[0001] This invention relates to porous plastic materials which compriseantiviral and/or antimicrobial agents, and to methods of making thesame.

2. BACKGROUND OF THE INVENTION

[0002] Porous materials can be used as vents or filters in innumerablemedical, research, consumer and industrial applications as.Unfortunately, the growth or accumulation of potentially harmful virusesor microbes (e.g., bacteria, fungi and protozoa) can occur in mostporous materials. In many applications, therefore, vents and filtersmust be changed frequently in order to prevent the accumulation and/orgrowth of viruses or microbes.

[0003] Antiviral and antimicrobial agents, which prevent the growth oraccumulation of viruses or microbes, have for some time beenincorporated into solid and fibrous materials. For example: U.S. Pat.No. 4,533,435 discloses the incorporation of an antimicrobial additiveinto the binding agent of a heavy-duty, kraft-type paper; U.S. Pat. No.4,430,381 discloses the incorporation of a salt of a monocarboxylateantimicrobial agent into an external binder system which is applied tofabrics and papers; U.S. Pat. No. 4,736,467 discloses operating roomgarments having a layer of baceriostatically-treated polyester/cottonfabric; U.S. Pat. No. 4,855,139 discloses a composition comprising acellulosic textile material that is chemically bonded to a fungicidallyactive phenolic compound; U.S. Pat. No. 5,069,907 discloses a surgicaldrape comprised of a synthetic polymeric film or fabric into which anantimicrobial agent has been incorporated; U.S. Pat. No. 5,091,102discloses a dry matrix for use in cleaning which comprises anantimicrobial compound; U.S. Pat. No. 5,639,464 discloses a biocidalpolymeric coating for heat exchanger coils; U.S. Pat. No. 5,853,883discloses fibers made from a melt-extrudable thermoplastic compositioncomprising an antimicrobial siloxane compound; U.S. Pat. No. 5,854,147discloses a non-woven web made from a melt-extrudable thermoplasticcomposition which comprises an antimicrobial siloxane compound; U.S.Pat. No. 5,894,042 discloses a conduit coating which comprises abacteriostatic, bacteriocidal, fungicidal, fungistatic ormildew-suppressing material; U.S. Pat. No. 5,919,554 discloses a fiberreinforced plastic comprising an antimicrobial composition; and U.S.Pat. No. 5,968,538 discloses a method of coating antiviral andantibacterial materials on a substrate material.

[0004] Although solid and fibrous materials comprising antiviral orantimicrobial agents can be used in some applications, they are oflittle use in applications that require a porous material that can bemolded into a particular shape, has a narrow distribution of pore sizes,or has high mechanical strength. Consequently, there exists a need forporous, non-fibrous materials that resist the accumulation or growth ofviruses and/or microbes.

3. SUMMARY OF THE INVENTION

[0005] This invention is directed to novel porous materials whichpossess antiviral and/or antimicrobial properties. Particular materialsof the invention comprise a porous thermoplastic substrate and anantiviral or antimicrobial agent. The invention is further directed tomethods of using the novel porous materials disclosed herein, as well asto vents and filters made of, or comprising, the novel porous materialsdisclosed herein.

[0006] Suitable thermoplastics that can be used to provide the porousthermoplastic substrate include, but are not limited to, polyolefins,nylons, polycarbonates, poly(ether sulfones), and mixtures thereof. Apreferred thermoplastic is a polyolefin. Examples of suitablepolyolefins include, but are not limited to: ethylene vinyl acetate;ethylene methyl acrylate; polyethylenes; polypropylenes;ethylene-propylene rubbers; ethylene-propylenediene rubbers;poly(1-butene); polystyrene; poly(2-butene); poly(1-pentene);poly(2-pentene); poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;polychloroprene; poly(vinyl acetate); poly(vinylidene chloride); andmixtures and derivatives thereof A preferred polyolefin is polyethylene.Examples of suitable polyethylenes include, but are not limited to, lowdensity polyethylene, linear low density polyethylene, high densitypolyethylene, ultra-high molecular weight polyethylene, and derivativesthereof.

[0007] The porous thermoplastic materials of the invention can furthercomprise materials such as, but not limited to, lubricants, colorants,fillers, and mixtures thereof. Suitable fillers include, but are notlimited to: carbon black, cellulose fiber powder, siliceous fillers,polyethylene fibers and filaments, and mixtures thereof.

[0008] Suitable antiviral or antimicrobial agents include, but are notlimited to: phenolic and chlorinated phenolic compounds; resorcinol andits derivatives; bisphenolic compounds; benzoic esters; halogenatedcarbanilides; polymeric antimicrobial agents; thazolines;trichloromethylthioimides; natural antimicrobial agents; metal salts;broad-spectrum antibiotics, and mixtures thereof. Preferred antiviral orantimicrobial agents include, but are not limited to:2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.

[0009] A first embodiment of the invention encompasses a porousthermoplastic material which comprises a sintered porous thermoplasticsubstrate having a surface at least part of which is coated with anantiviral or antimicrobial agent.

[0010] Although the thermoplastic substrate can be made of anythermoplastic, including those disclosed herein, it is preferably madeof polyethylene, more preferably ultra-high molecular weightpolyethylene. Preferred antiviral or antimicrobial agents include, butare not limited to, 2,4,4′-trichloro-2′-hydroxy-diphenyl ether,3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea, poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride), silver ions, andsalts and mixtures thereof.

[0011] A specific porous material of the invention thus comprises: asintered porous polyethylene substrate; an antiviral or antimicrobialagent selected from the group consisting of2,4,4′-trichloro-2′-hydroxy-diphenyl ether,3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea, poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride), silver ions, andsalts and mixtures thereof; and an optional filler, wherein the sinteredporous polyethylene substrate has a surface at least part of which iscoated with the antiviral or antimicrobial agent.

[0012] Another specific porous material of the invention comprises asintered porous polyethylene core and a coating layer disposed over atleast part of the porous polyethylene core. Preferably, the coatinglayer further comprises a thermoplastic or hydrogel material. Suitablethermoplastic or hydrogel materials include, but are not limited to,polyurethanes such as hydrophilic polyurethane.

[0013] A second embodiment of the invention encompasses a porousmaterial which comprises a sintered porous thermoplastic substrate andan antiviral or antimicrobial agent disposed throughout at least part ofthe substrate.

[0014] Although the thermoplastic substrate can be made of anythermoplastic, including those disclosed herein, it is it is preferablypolyethylene. Preferred antiviral or antimicrobial agents include, butare not limited to, 2,4,4′-trichloro-2′-hydroxy-diphenyl ether,3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea, poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride), silver ions, andsalts and mixtures thereof.

[0015] A specific porous material of the invention thus comprises asintered porous polyethylene substrate and an antiviral or antimicrobialagent disposed within at least part of the sintered porous polyethylenesubstrate, wherein the antiviral or antimicrobial agent is selected fromthe group consisting of: 2,4,4′-trichloro-2′-hydroxy-diphenyl ether,3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea, poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride), silver ions, andsalts and mixtures thereof. In an even more specific material of theinvention, the antiviral or antimicrobial agent is disposed uniformlywithin at least about 75 percent, more preferably at least about 90percent, and most preferably at least about 95 percent of the porouspolyethylene substrate.

[0016] A third embodiment of the invention encompasses a particlecomprising an antiviral or antimicrobial agent disposed within and/or onthe surface of a thermoplastic core. A preferred particle has a diameterof from about 5 μM to about 1000 μM, more preferably from about 10 μM toabout 500 μM, and most preferably from about 20 μM to about 300 μM.Suitable thermoplastics from which the core can be made include, but arenot limited to, polyolefins, nylons, polycarbonates, poly(ethersulfones), and mixtures thereof. A preferred thermoplastic is apolyolefin. A preferred polyolefin is polyethylene. Examples of suitablepolyethylenes are disclosed herein. Suitable antiviral or antimicrobialagents are described herein. Preferred antiviral or antimicrobial agentsinclude, but are not limited to: 2,4,4′-trichloro-2′-hydroxy-diphenylether; 3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylenehydrochloride); silver ions; and salts and mixtures thereof.

[0017] A fourth embodiment of the invention encompasses a process formaking a porous thermoplastic material and the products of the process.The process comprises contacting a sintered porous substrate with anantiviral or antimicrobial agent. Preferably, the porous substrate ismade of polyethylene, more preferably high-density polyethylene.Suitable antiviral or antimicrobial agents are described herein.Preferred antiviral or antimicrobial agents include, but are not limitedto: 2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.

[0018] A fifth embodiment of the invention encompasses a process formaking a particle and the products of that process. The processcomprises cooling a molten pre-particle, wherein the pre-particle iscomprised of a thermoplastic and an antiviral or antimicrobial agent.Preferably, the molten pre-particle is formed by chopping a moltenextrudate. Preferably, the antiviral or antimicrobial agent is selectedfrom the group consisting of: 2,4,4′-trichloro-2′-hydroxy-diphenylether; 3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylenehydrochloride); silver ions; and salts and mixtures thereof.

[0019] A sixth embodiment of the invention encompasses another processfor making a porous thermoplastic material and the products of theprocess. The process comprises contacting a sintered porous substratewith a coating mixture which comprises an antiviral or antimicrobialagent. Preferably, the coating mixture further comprises a thermoplasticor hydrogel material. Suitable thermoplastic or hydrogel materialsinclude, but are not limited to, polyurethanes such as hydrophilicpolyurethane. Preferably, the porous substrate is made of polyethylene,more preferably high-density polyethylene. Suitable antiviral orantimicrobial agents are described herein. Preferred antiviral orantimicrobial agents include, but are not limited to:2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.

[0020] A seventh embodiment of the invention encompasses another processfor making a porous thermoplastic material and the products of theprocess. The process comprises sintering particles which are comprisedof an antiviral or antimicrobial agent disposed about a thermoplasticcore. Preferred thermoplastics are disclosed herein. A particularlypreferred thermoplastic is polyethylene. Suitable antiviral orantimicrobial agents are described herein. Preferred antiviral orantimicrobial agents include, but are not limited to:2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.

3.1. Definitions

[0021] As used herein to describe a particle, the term “substantiallyspherical” means that the particle is spherical or that the length ofits longest radius is no greater than about 2.0 times, more preferablyno greater than about 1.5 times, even more preferably no greater thanabout 1.2 times the length of its shortest radius. When used to describea mixture or collection of particles, the term “substantially spherical”means that greater than about 50%, more preferably greater than about75%, even more preferably greater than about 90%, and most preferablygreater than about 95% of the particles are substantially spherical.

[0022] As used herein, the term “substantial portion” means greater thanabout 80%, more preferably greater than about 90%, and most preferablygreater than about 95%.

[0023] As used herein, the terms “degradation temperature” and“decomposition temperature” mean the temperature at which a particularchemical compound (e.g., an antiviral or antimicrobial agent) decomposesor loses its ability to retard the growth or kill a virus or microbe. Asthose skilled in the art will recognize, the degradation temperature ofa particular material will vary as a function of, for example, pressureand exposure to oxidants, reductants, or other reactive chemicalmoieties.

[0024] As used herein, the term “substantial degradation” means thedegradation of a substantial portion of the material described.

[0025] As used herein to describe a compound or moiety, the term“derivative” means a compound or moiety wherein the degree of saturationof at least one bond has been changed (e.g., a single bond has beenchanged to a double or triple bond) or wherein at least one hydrogenatom has been replaced with a different atom or with a chemical moiety.Examples of different atoms and chemical moieties include, but are notlimited to, alkyl, aryl, halogen, oxygen, nitrogen, sulfur, hydroxy,methoxy, alkyl, amine, amide, ketone, and aldehyde.

4. DETAILED DESCRIPTION OF THE INVENTION

[0026] This invention is directed to novel porous materials which resistthe accumulation or growth of viruses and/or microbes. The novelmaterials of the invention can be molded or formed into any of a varietyof shapes, and can thus be used to provide, for example, filters orvents suitable for use in a variety of medical, research, consumer andindustrial applications. The mechanical strength and uniform porosity ofspecific materials of the invention further enable their use inapplications for which fibrous materials, such as papers and fabrics,are not suited.

[0027] The porous materials of the invention comprise a porous substrateand at least one antiviral or antimicrobial agent, examples of which areprovided in Section 4.1.

4.1. Materials

[0028] Using methods such as those described herein, the poroussubstrates of the materials of the invention are made from at least onetype of thermoplastic. Examples of suitable thermoplastics include, butare not limited to, polyolefins, nylons, polycarbonates, and poly(ethersulfones). Preferred thermoplastics are polyolefins.

[0029] Examples of polyolefins suitable for use in the inventioninclude, but are not limited to: ethylene vinyl acetate (EVA); ethylenemethyl acrylate (EMA); polyethylenes such as, but not limited to, lowdensity polyethylene (LDPE), linear low density polyethylene (LLDPE),high density polyethylene (HDPE), and ultra-high molecular weightpolyethylene (UHMWPE); polypropylenes; ethylene-propylene rubbers;ethylene-propylene-diene rubbers; poly(1-butene); polystyrene;poly(2-butene); poly(1-pentene); poly(2-pentene);poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;polychloroprene; poly(vinyl acetate); poly(vinylidene chloride); andmixtures and derivatives thereof. Specific EVA materials include, butare not limited to, those in the Microthene MU® and Microthene FE®series manufactured by Equistar, Houston, Tex., such as Microthene MU763-00 (9% vinyl acetate) and Microthene FE 532-00 (9% vinyl acetate).Specific EMA materials include, but are not limited to, those in theOptema TC® series manufactured by Exxon Chemical Company, Baton Rouge,La., such as Optema TC-110 (21.5% methyl acrylate). Specificpolyethylene materials include, but are not limited to, those in theExact® series manufactured by Exxon Chemical Company, such as ExactSLX-9090, Exact 3024, Exact, 3030, Exact 3033, Exact 4011, Exact 4041,Exact SLP-9053, Exact SLP-9072, and Exact SLP-9095. Specific examples ofLDPE include, but are not limited to, those in the 20 seriesmanufactured by DuPont Chemical Company, Wilmington, Del., such as 20series 20, 20 series 20-6064, 20 series 2005, 20 series 2010, and 20series 2020T. Specific examples of LLDPE include, but are not limitedto, those in the Exact® series manufactured by Exxon Chemical Company,such as Exact 3022 and Exact 4006. Specific examples of HDPE include,but are not limited to, those in the Escorene HX® series manufactured byExxon Chemical Company, such as Escorene HX-0358.

[0030] Ultra-high molecular weight polyethylenes suitable for use in theinvention include, but are not limited to, UHMWPE having a molecularweight greater than about 1,000,000. Typically, UHMWPE displays nomeasurable flow rate under normal test procedures. See, U.S. Pat. No.3,954,927. Ultra-high molecular weight polyethylene also tends to haveenhanced mechanical properties compared to other polyethylenes,including, but not limited to, abrasion resistance, impact resistanceand toughness. Polyethylenes having weight average molecular weights of1,000,000 or higher, which are included within the class designated asUHMWPE, typically an intrinsic viscosity in the range of about 8 ormore. Specific examples of UHMWPE include, but are not limited to,Hostalen GUR® sold by Ticona Inc., League City, Tex.

[0031] Polypropylenes suitable for use in the invention include, but arenot limited to: the Polyfort® series manufactured by A Shulman Co.,Akron, Ohio, such as FPP 2320E, 2321E, 2322E, 2345E, PP2130, and PP2258;the Acctuf® series manufactured by BP Amoco Corporation, Atlanta, Ga.,such as Acctuf 3045, Amoco 6014, and Amoco 6015; the Aristech® seriesmanufactured by Aristech Chemical Corp., Pittsburgh, Pa., such asD-007-2, LP-230-S, and TI-4007-A; the Borealis® series manufactured byBASF Thermoplastic Materials, Saint Paul, Minn., such as BA101E, BA110E,BA122B, BA204E, BA202E, and BA124B; the Polypro® series manufactured byChisso America Inc., Schaumburg, Ill., such as F1177 and F3020; theNoblen® series manufactured by Mitsubishi Petrochemical Co. Ltd., Tokyo,Japan, such as MA8; the Astryn® series manufactured by Montell USA Inc.,Wilmington, Del., such as 68F4-4 and PD451; the Moplen® seriesmanufactured by Montell USA Inc., such as D 50S, D 60P, and D 78PJ; andthe Pro-Fax® series manufactured by Montell USA Inc., such as 6723,6823, and 6824.

[0032] Sinterable thermoplastics in addition to those recited herein canalso be used in this invention. As those skilled in the art are wellaware, the ability of a thermoplastic to be sintered can be determinedfrom its melt flow index (MFI). Melt flow indices of individualthermoplastics are known or can be readily determined by methods wellknown to those skilled in the art. For example, the extrusionplastometer made by Tinius Olsen Testing Machine Company, Willow Grove,Pa., can be used. As discussed elsewhere herein, the MFIs ofthermoplastics suitable for use in this invention will depend on theparticular porous thermoplastic material and/or the method used toprepare it. In general, however, the MFI of a thermoplastic suitable foruse in the materials and methods of the invention is from about 0 toabout 15, more preferably from about 0.2 to about 12, and mostpreferably from about 0.5 to about 10. The temperatures at whichindividual thermoplastics sinter (i.e., their sintering temperatures)are also well known, or can be readily determined by routine methodssuch as, but not limited to, thermal mechanical analysis and dynamicmechanical thermal analysis.

[0033] The novel materials of the invention next comprise at least oneantiviral or antimicrobial agent. Antiviral and antimicrobial agentsthat can be used in the methods and materials of this invention includeagents that kill viruses or microbes as well as agents that simplyinhibit their growth or accumulation. For health reasons, antiviral orantimicrobial agents that inhibit the growth of microbes are preferablyused for materials that are to be used in, for example, consumerproducts.

[0034] Examples of antiviral and antimicrobial agents that can be usedin the materials and methods of the invention include, but are notlimited to, phenolic and chlorinated phenolic compounds, resorcinol andits derivatives, bisphenolic compounds, benzoic esters (parabens),halogenated carbonilides, polymeric antimicrobial agents, thazolines,trichloromethylthioimides, natural antimicrobial agents (also referredto as “natural essential oils”), metal salts, and broad-spectrumantibiotics.

[0035] Specific phenolic and chlorinated phenolic antiviral andantimicrobial agents that can be used in the invention include, but arenot limited to: phenol; 2-methyl phenol; 3-methyl phenol; 4-methylphenol; 4-ethyl phenol; 2,4-dimethyl phenol; 2,5-dimethyl phenol;3,4-dimethyl phenol; 2,6-dimethyl phenol; 4-n-propyl phenol; 4-n-butylphenol; 4-n-amyl phenol; 4-tert-amyl phenol; 4-n-hexyl phenol;4-n-heptyl phenol; mono- and poly-alkyl and aromatic halophenols;p-chlorophenyl; methyl p-chlorophenol; ethyl p-chlorophenol; n-propylp-chlorophenol; n-butyl p-chlorophenol; n-amyl p-chlorophenol; sec-amylp-chlorophenol; n-hexyl p-chlorophenol; cyclohexyl p-chlorophenol;n-heptyl p-chlorophenol; n-octyl; p-chlorophenol; o-chlorophenol; methylo-chlorophenol; ethyl o-chlorophenol; n-propyl o-chlorophenol; n-butylo-chlorophenol; n-amyl o-chlorophenol; tert-amyl o-chlorophenol; n-hexylo-chlorophenol; n-heptyl o-chlorophenol; o-benzyl p-chlorophenol;o-benxyl-m-methyl p-chlorophenol; o-benzyl-m,m-dimethyl p-chlorophenol;o-phenylethyl p-chlorophenol; o-phenylethyl-m-methyl p-chlorophenol;3-methyl p-chlorophenol 3,5-dimethyl p-chlorophenol, 6-ethyl-3-methylp-chlorophenol, 6-n-propyl-3-methyl p-chlorophenol;6-iso-propyl-3-methyl p-chlorophenol; 2-ethyl-3,5-dimethylp-chlorophenol; 6-sec-butyl-3-methyl p-chlorophenol;2-iso-propyl-3,5-dimethyl p-chlorophenol; 6-diethylmethyl-3-methylp-chlorophenol; 6-iso-propyl-2-ethyl-3-methyl p-chlorophenol;2-sec-amyl-3,5-dimethyl p-chlorophenol; 2-diethylmethyl-3,5-dimethylp-chlorophenol; 6-sec-octyl-3-methyl p-chlorophenol; p-chloro-m-cresolp-bromophenol; methyl p-bromophenol; ethyl p-bromophenol; n-propylp-bromophenol; n-butyl p-bromophenol; n-amyl p-bromophenol; sec-amylp-bromophenol; n-hexyl p-bromophenol; cyclohexyl p-bromophenol;o-bromophenol; tert-amyl o-bromophenol; n-hexyl o-bromophenol;n-propyl-m,m-dimethyl o-bromophenol; 2-phenyl phenol; 4-chloro-2-methylphenol; 4-chloro-3-methyl phenol; 4-chloro-3,5-dimethyl phenol;2,4-dichloro-3,5-dimethylphenol; 3,4,5,6-tetabromo-2-methylphenol;5-methyl-2-pentylphenol; 4-isopropyl-3-methylphenol;para-chloro-metaxylenol (PCMX); chlorothymol; phenoxyethanol;phenoxyisopropanol; and 5-chloro-2-hydroxydiphenylmethane.

[0036] Resorcinol and its derivatives can also be used as antiviral orantimicrobial agents. Specific resorcinol derivatives include, but arenot limited to: methyl resorcinol; ethyl resorcinol; n-propylresorcinol; n-butyl resorcinol; n-amyl resorcinol; n-hexyl resorcinol;n-heptyl resorcinol; n-octyl resorcinol; n-nonyl resorcinol; phenylresorcinol; benzyl resorcinol; phenylethyl resorcinol; phenylpropylresorcinol; p-chlorobenzyl resorcinol; 5-chloro-2,4-dihydroxydiphenylmethane; 4′-chloro-2,4-dihydroxydiphenyl methane;5-bromo-2,4-dihydroxydiphenyl methane; and4′-bromo-2,4-dihydroxydiphenyl methane.

[0037] Specific bisphenolic antiviral and antimicrobial agents that canbe used in the invention include, but are not limited to: 2,2′-methylenebis-(4-chlorophenol); 2,4,4′trichloro-2′-hydroxy-diphenyl ether, whichis sold by Ciba Geigy, Florham Park, N.J. under the tradenameTriclosan®; 2,2′-methylene bis-(3,4,6-trichlorophenol); 2,2′-methylenebis-(4-chloro-6-bromophenol); bis-(2-hydroxy-3,5-dichlorophenyl)sulphide; and bis-(2-hydroxy-5-chlorobenzyl)sulphide.

[0038] Specific benzoie esters (parabens) that can be used in theinvention include, but are not limited to: methylparaben; propylparaben;butylparaben; ethylparaben; isopropylparaben; isobutylparaben;benzylparaben; sodium methylparaben; and sodium propylparaben.

[0039] Specific halogenated carbanilides that can be used in theinvention include, but are not limited to: 3,4,4′-trichlorocarbanilides,such as 3-(4-chlorophenyl)-1-(3,4-dichlorphenyl)urea sold under thetradename Triclocarban® by Ciba-Geigy, Florham Park, N.J.;3-trifluoromethyl-4,4′-dichlorocarbanilide; and3,3′,4-trichlorocarbanilide.

[0040] Specific polymeric antiviral and antimicrobial agents that can beused in the invention include, but are not limited to: polyhexamethylenebiguanide hydrochloride; and poly(iminoimidocarbonyl iminoimidocarbonyliminohexamethylene hydrochloride), which is sold under the tradenameVantocil® IB.

[0041] Specific thazolines that can be used in the invention include,but are not limited to that sold under the tradename Micro-Check®; and2-n-octyl-4-isothiazolin-3-one, which is sold under the tradenameVinyzene® IT-3000 DIDP.

[0042] Specific trichloromethylthioimides that can be used in theinvention include, but are not limited to:N-(trichloromethylthio)phthalimide, which is sold under the tradenameFungitrol®; and N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide,which is sold under the tradename Vancide®.

[0043] Specific natural antimicrobial agents that can be used in theinvention include, but are not limited to, oils of: anise; lemon;orange; rosemary; wintergreen; thyme; lavender; cloves; hops; tea tree;citronella; wheat; barley; lemongrass; cedar leaf; cedarwood; cinnamon;fleagrass; geranium; sandalwood; violet; cranberry; eucalyptus; vervain;peppermint; gum benzoin; basil; fennel; fir; balsam; menthol; ocmeaoriganuin; hydastis; carradensis; Berberidaceac daceae; Ratanhiae longa;and Curcuma longa. Also included in this class of natural antimicrobialagents are the key chemical components of the plant oils which have beenfound to provide antimicrobial benefit. These chemicals include, but arenot limited to: anethol; catechole; camphene; thymol; eugenol;eucalyptol; ferulic acid; farnesol; hinokitiol; tropolone; limonene;menthol; methyl salicylate; carvacol; terpineol; verbenone; berberine;ratanhiae extract; caryophellene oxide; citronellic acid; curcumin;nerolidol; and geraniol.

[0044] Specific metal salts that can be used in the invention include,but are not limited to, salts of metals in groups 3a-5a, 3b-7b, and 8 ofthe periodic table. Specific examples of metal salts include, but arenot limited to, salts of: aluminum; zirconium; zinc; silver; gold;copper; lanthanum; tin; mercury; bismuth; selenium; strontium; scandium;yttrium; cerium; praseodymiun; neodymium; promethum; samarium; europium;gadolinium; terbium; dysprosium; holmium; erbium; thalium; ytterbium;lutetium; and mixtures thereof. A preferred metal-ion basedantimicrobial agent is sold under the tradename HealthShield®, and ismanufactured by HealthShield Technology, Wakefield, Mass.

[0045] Specific broad-spectrum antimicrobial agents that can be used inthe invention include, but are not limited to, those that are recited inother categories of antiviral or antimicrobial agents herein.

[0046] Additional antiviral or antimicrobial agents that can be used inthe processes and materials of the invention include, but are notlimited to: pyrithiones, and in particular pyrithione-including zinccomplexes such as that sold under the tradename Octopirox®;dimethyidimethylol hydantoin, which is sold under the tradenameGlydant®; methylchloroisothiazolinone/methylisothiazolinone, which issold under the tradename Kathon CG®; sodium sulfite; sodium bisulfite;imidazolidinyl urea, which is sold under the tradename Germall 115®;diazolidinyl urea, which is sold under the tradename Germall 11®; benzylalcohol v2-bromo-2-nitropropane-1,3-diol, which is sold under thetradename Bronopol®; formalin or formaldehyde; iodopropenylbutylcarbamate, which is sold under the tradename Polyphase P100®;chloroacetamide; methanamine; methyldibromonitrile glutaronitrile(1,2-dibromo-2,4-dicyanobutane), which is sold under the tradenameTektamer®; glutaraldehyde; 5-bromo-5-nitro-1,3-dioxane, which is soldunder the tradename Bronidox®; phenethyl alcohol; o-phenylphenol/sodiumo-phenylphenol sodium hydroxymethylglycinate, which is sold under thetradename Suttocide A®; polymethoxy bicyclic oxazolidine; which is soldunder the tradename Nuosept C®; dimethoxane; thimersal; dichlorobenzylalcohol; captan; chlorphenenesin; dichlorophene; chlorbutanol; glyceryllaurate; halogenated diphenyl ethers;2,4,4′-trichloro-2′-hydroxy-diphenyl ether, which is sold under thetradename Triclosan® and is available from Ciba-Geigy, Florham Park,N.J.; and 2,2′-dihydroxy-5,5′-dibromo-diphenyl ether.

[0047] Additional antiviral and antimicrobial agents that can be used inthe materials and methods of the invention include those disclosed byU.S. Pat. Nos. 3,141,321; 4,402,959; 4,430,381; 4,533,435; 4,625,026;4,736,467; 4,855,139; 5,069,907; 5,091,102; 5,639,464; 5,853,883;5,854,147; 5,894,042; and 5,919,554, all of which are incorporatedherein by reference.

[0048] Specific antiviral or antimicrobial agents that are preferablyused in the materials or methods of this invention include, but are notlimited to, those sold under the tradenames Triclosan®, Triclocarban®,Vantocil® IB, and HealthShield®. A particularly preferred antiviral orantimicrobial agent is sold under the tradename Triclosan®.

[0049] The porous virus- or microbe-resistant materials of the inventioncan optionally comprise additional materials such as, but not limitedto, lubricants, colorants, and fillers. Examples of fillers include, butare not limited to, carbon black, cellulose fiber powder, siliceousfillers, polyethylene fibers and filaments, and mixtures thereof.Specific polyethylene fibers and filaments include, but are not limitedto, those disclosed by U.S. Pat. Nos. 5,093,197 and 5,126,219, both ofwhich are incorporated herein by reference.

[0050] Using the materials described herein, the novel porousthermoplastic media of the invention can be made using one of theprocesses of the invention. In a first process of the invention, aporous thermoplastic substrate is contacted with at least one antiviralor antimicrobial agent. In a second process of the invention, a porousthermoplastic substrate is contacted with a coating mixture whichcomprises at least one antiviral or antimicrobial agent. In a thirdprocess of the invention, thermoplastic particles which comprise atleast one antiviral or antimicrobial agent are sintered together.

4.2. Coating- or Impregnation-Based Methods

[0051] In two processes of the invention, a porous thermoplasticsubstrate is contacted with at least one antiviral or antimicrobialagent. In a first process, an antiviral or antimicrobial agent alone orin solution is contacted with the substrate, thereby coating and/orimpregnating at least part of the substrate with the agent. In a secondprocess, the porous substrate is contacted with a coating mixture thatcomprises an antiviral or antimicrobial agent and an additional materialthat will coat and/or impregnate the porous substrate. In both methods,the porous substrate is first prepared, preferably by sintering togetherthermoplastic particles.

[0052] The thermoplastic particles used to provide a porous substratepreferably have an average diameter of from about 5 μM to about 1000 μM,more preferably from about 10 μM to about 500 μM, and most preferablyfrom about 20 μM to about 300 μM. It is also preferred that theparticles used to form the porous substrate are all of about the samesize. In other words, it is preferred that the particles' sizedistribution be narrow (e.g., as determined using commercially availablescreens). It has been found that particles of about the same size can beconsistently packed into molds. A narrow particle size distributionfurther allows the production of a substrate with uniform porosity(i.e., a substrate comprising pores that are evenly distributedthroughout it and/or are of about the same size). This is advantageousbecause solutions and gases tend to flow more evenly through uniformlyporous filters and vents than through filters and vents which containregions of high and low permeability. Uniformly porous substrates arealso less likely to have structural weak spots than substrates whichcomprise unevenly distributed pores of substantially different sizes. Inview of these benefits, if a thermoplastic is commercially available inpowder (i.e., particulate) form, it is preferably-screened prior to useto ensure a desired average size and size distribution. However, mostthermoplastics are not commercially available in powder form, and musttherefore be converted into powder form by methods well known to thoseskilled in the art such as, but not limited to, cryogenic grinding andunderwater pelletizing.

[0053] Cryogenic grinding can be used to prepare thermoplastic particlesof varying sizes. But because cryogenic grinding provides little controlover the sizes of the particles it produces, powders formed using thistechnique may be screened to ensure that the particles to be sinteredare of a desired average size and size distribution.

[0054] Underwater pelletizing can also be used to form thermoplasticparticles suitable for sintering. Although typically limited to theproduction of particles having diameters of greater than about 36 μM,underwater pelletizing offers several advantages. First, it providesaccurate control over the average size of the particles produced, inmany cases thereby eliminating the need for an additional screening stepand reducing the amount of wasted material. A second advantage ofunderwater pelletizing, which is discussed further herein, is that itallows significant control over the particles' shape.

[0055] Underwater pelletizing is described, for example, in U.S. patentapplication Ser. No. 09/064,786, filed Apr. 23, 1998, and U.S.provisional patent application No. 60/044,238, filed Apr. 24, 1999, bothof which are incorporated herein by reference. Thermoplastic particleformation using underwater pelletizing typically requires an extruder ormelt pump, an underwater pelletizer, and a drier. The thermoplasticresin is fed into an extruder or a melt pump and heated untilsemi-molten. The semi-molten material is then forced through a die. Asthe material emerges from the die, at least one rotating blade cuts itinto pieces herein referred to as “pre-particles.” The rate of extrusionand the speed of the rotating blade(s) determine the shape of theparticles formed from the pre-particles, while the diameter of the dieholes determine their average size. Water, or some other liquid or gascapable of increasing the rate at which the pre-particles cool, flowsover the cutting blade(s) and through the cutting chamber. Thiscoagulates the cut material (i.e., the pre-particles) into particles,which are then separated from the coolant (e.g., water), dried, andexpelled into a holding container.

[0056] The average size of particles produced by underwater pelletizingcan be accurately controlled and can range from about 0.014″ (35.6 μM)to about 0.125″ (318 μM) in diameter, depending upon the thermoplastic.Average particle size can be adjusted simply by changing dies, withlarger pore dies yielding proportionally larger particles. The averageshape of the particles can be optimized by manipulating the extrusionrate and the temperature of the water used in the process.

[0057] While the characteristics of a porous material can depend on theaverage size and size distribution of the particles used to make it,they can also be affected by the particles' average shape. Consequently,in another embodiment of the invention, the thermoplastic particles aresubstantially spherical. This shape provides specific benefits. First,it facilitates the efficient packing of the particles within a mold.Second, substantially spherical particles, and in particular those withsmooth edges, tend to sinter evenly over a well defined temperaturerange to provide a final product with desirable mechanical propertiesand porosity.

[0058] In a specific embodiment of the invention, the thermoplasticparticles are substantially spherical and free of rough edges.Consequently, if the thermoplastic particles used in this preferredmethod are commercially available, they are thermal fined to ensuresmooth edges and screened to ensure a proper average size and sizedistribution. Thermal fining, which is well known to those skilled inthe art, is a process wherein particles are rapidly mixed and optionallyheated such that their rough edges become smooth. Mixers suitable forthermal fining include the W series high-intensity mixers available fromLittleford Day, Inc., Florence, Ky.

[0059] Thermoplastic particles made using cryogenic grinding arelikewise preferably thermal fined to ensure smooth edges and screened toensure a proper average size and size distribution. Advantageously,however, if the particles are made using underwater pelletizing, whichallows precise control over particle size and typically provides smooth,substantially spherical particles, subsequent thermal fining andscreening need not be performed.

[0060] Once thermoplastic particles of a desired average size and/orshape have been obtained, they are optionally combined with additionalmaterials such as, but not limited to, lubricants, colorants, andfillers such as those described above in Section 4.1. As those skilledin the art will recognize, the types and amounts of optional materialsincorporated into a porous substrate will typically depend on theapplication for which the final antiviral or antimicrobial material willbe used.

[0061] After the thermoplastic particles and optional additionalmaterials have been blended, preferably to provide a uniform mixture,the mixture is sintered. Depending on the desired size and shape of thefinal product (e.g., a block, tube, cone, cylinder, sheet, or membrane),this can be accomplished using a mold, a belt line such as thatdisclosed by U.S. Pat. No. 3,405,206, which is hereby incorporated byreference, or using other techniques known to those skilled in the art.In a preferred embodiment of the invention, the mixture is sintered in amold. Suitable molds are commercially available and are well known tothose skilled in the art. Specific examples of molds include, but arenot limited to, flat sheets with thickness ranging from about ⅛ inch toabout 0.5 inch, round cylinders of varying heights and diameters, andsmall conical parts molded to fit snugly into a pipette tip. Suitablemold materials include, but are not limited to, metals and alloys suchas aluminum and stainless steel, high temperature thermoplastics, andother materials both known in the art and disclosed herein.

[0062] In a specific preferred embodiment of the invention, acompression mold is used to provide the sintered material. In thisembodiment, the mold is heated to the sintering temperature, allowed toequilibrate, and then subjected to pressure. This pressure typicallyranges from about 1 psi to about 10 psi, depending on the composition ofthe mixture being sintered and the desired porosity of the finalproduct. In general, the greater the pressure applied to the mold, thesmaller the average pore size and the greater the mechanical strength ofthe final product. The duration of time during which the pressure isapplied also varies depending on the desired porosity of the finalproduct, and is typically from about 2 to about 10, more typically fromabout 4 to about 6 minutes. In another embodiment of the invention, thethermoplastic particles are sintered in a mold without the applicationof pressure.

[0063] Once the porous substrate has been formed, the mold is allowed tocool. If pressure has been applied to the mold, the cooling can occurwhile it is still being applied or after it has been removed. Thesubstrate is then removed from the mold and optionally processed.Examples of optional processing include, but are not limited to,sterilizing, cutting, milling, polishing, encapsulating, and coating.The substrate is then coated and/or impregnated with at least oneantiviral or antimicrobial agent, or a mixture comprising at least oneantiviral or antimicrobial agent, as described below in Section 4.2.1 or4.2.2.

4.2.1. Use of an Antiviral or Antimicrobial Agent Alone or in Solution

[0064] In a first method of the invention, the porous thermoplasticsubstrate is contacted with the antiviral or antimicrobial agent or amixture which comprises it. Any method of coating or impregnation knownto those skilled in the art can be used. For example, the thermoplasticsubstrate can be dipped or immersed in a liquid antiviral orantimicrobial agent, or in a solution comprising an antiviral orantimicrobial agent, and then allowed to dry. Alternatively, anantiviral or antimicrobial agent or a solution comprising an antiviralor antimicrobial agent can be sprayed onto the substrate.

[0065] The resulting porous thermoplastic coated or impregnated materialis then optionally further processed. Examples of further processinginclude, but are not limited to, sterilizing, cutting, milling,polishing, encapsulating, and coating.

[0066] 4.2.2. Coating or Impregnating with a Coating Mixture

[0067] In a second process of the invention, the porous substrate iscontacted with a coating mixture that comprises an antiviral orantimicrobial agent and an additional material that will coat and/orimpregnate the porous substrate. Thus, one embodiment of the inventionprovides a product with a porous thermoplastic core surround at least inpart by a coating layer which comprises an antiviral or antimicrobialagent.

[0068] This second process of the invention provides several advantages.First, it allows higher concentrations of antiviral or antimicrobialagent to be located near or on the surface of the final product. Thiscan, for example, allow for a rapid release of the agent into thesurrounding environment. Second, this process can used to minimize thedifference between the surface energy of the porous substrate and thelayer of antiviral or antimicrobial agent that covers at least part ofit. Third, the process allows certain porous substrates to be coatedwith antiviral or antimicrobial agents that would otherwise not adhereto those substrates.

[0069] Examples of additional materials that can be combined with anantiviral or antimicrobial agent according to this process includethermoplastics such as those disclosed herein and hydrogels. Examples ofhydrogels that can be used in this invention include those disclosed inU.S. patent application Ser. No. 09/305,083, filed May 4, 1999, which isincorporated herein by reference. Preferred additional materials arepolyurethanes or derivatives thereof, and hydrophilic polyurethane inparticular.

[0070] In a specific embodiment, the coating mixture is, or comprises, acommercially available thermoplastic resin which already comprises anantiviral or antimicrobial agent, such as those described below inSection 4.3.

[0071] The porous substrate can be contacted with the antiviral orantimicrobial mixture using any techniques known to those skilled in theart, including those described in Section 4.2.1 above. After the porousthermoplastic substrate has been contacted with the antiviral orantimicrobial mixture such that the mixture coats and/or impregnates atleast part of the substrate, the resulting material can be dried, curedor otherwise treated. For example, chemical or radiation-inducedcrosslinking of the molecules within the coating mixture can be used toform a hard, durable coating.

[0072] The resulting porous thermoplastic coated or impregnated materialis then optionally further processed. Examples of further processinginclude, but are not limited to, sterilizing, cutting, milling,polishing, encapsulating, and coating.

4.3. Sintering-Based Impregnation and Coating Methods

[0073] In a third process of the invention, an antiviral orantimicrobial agent is incorporated into the porous thermoplasticsubstrate during, rather than after, the sintering process. This processprovides several advantages. First, it can be used to locate antiviralor antimicrobial agents within the porous material, and in particular atplaces or depths within the material that may be inaccessible usingdipping or coating methods. Second, this process can be used to ensurethat the distribution of antiviral or antimicrobial agent(s) within thefinal material is uniform; e.g., that the density of an antiviral orantimicrobial agent is uniform throughout the material. A thirdadvantage of this process is that it can be used to trap large antiviralor antimicrobial agents within pores that have small openings, as wellas large amounts of antiviral or antimicrobial agents. A final advantageof this process is that it allows the use of commercially availableconcentrates that already contain antiviral or antimicrobial agents.

[0074] This process of the invention comprises the sintering ofthermoplastic particles which comprise at least one antiviral orantimicrobial agent (referred to herein as “thermoplastic antiviral orantimicrobial particles” or “PAA particles”), optionally withthermoplastic particles which do not comprise antiviral or antimicrobialagents and/or additional materials such as those described above inSection 4.1.

[0075] In a first specific embodiment of this process, a thermoplasticresin comprising at least one antiviral or antimicrobial agent iscryogenically ground and optionally screened and/or thermal fined toprovide particles which can be sintered as described above in Section4.2. In a specific embodiment of this process, each of the PAA particlesis approximately the same size. In another specific embodiment of thisprocess, the PAA particles are substantially spherical.

[0076] Thermoplastic resins which comprise antiviral or antimicrobialagents (herein referred to as “PAA resins”) such as Microban® 4010-100are commercially available from, for example, Microban Products Company,Huntersville, N.C. Because these resins typically contain large amountsof antiviral or antimicrobial agents, it may be desirable to combine PAAparticles formed from them with other thermoplastic particles that donot contain antiviral or antimicrobial agents in order to provide porousmaterials with lower average concentrations of antiviral orantimicrobial agent. In such cases, it is preferred that thethermoplastic particles are of about the same size as the PAA particles.In some cases, it may also be preferred that all of the particles to besintered are substantially spherical. As discussed above in Section 4.2,this can help provide a final product having uniform porosity and goodmechanical characteristics.

[0077] If the PAA particles are combined with particles of otherthermoplastics and/or other materials such as lubricants, colorants andfillers, it is preferred that the combination be mixed to ensure thatthe components are evenly distributed. The resulting mixture is thensintered to provide a porous material that resists the accumulation orgrowth of viruses and/or microbes.

[0078] Suitable sintering conditions are known in the art and include,for example, those described above in Section 4.2. However, because someantiviral or antimicrobial agents may decompose under particularsintering conditions, those skilled in the art will recognize that thethermoplastic, the sintering conditions, and/or the antiviral orantimicrobial agent will have to be selected to provide a porousthermoplastic product of the invention that is capable of resisting thegrowth or accumulation of viruses or microbes to a desired degree. Forexample, a thermoplastic with a low MFI or sintering temperature can beselected such that the sintering temperature will not cause thedecomposition of a desired antiviral or antimicrobial agent.Alternatively, a temperature-resistant antiviral or antimicrobial agent(e.g., a metal-ion based agent such as HealthShield®) may be selected ifthe preferred thermoplastic sinters only at high temperatures.

[0079] In a second specific embodiment of this process, PAA particlesare formed by underwater pelletizing. Although typically not necessary,the resulting PAA particles can optionally be screened and/or thermalfined. Underwater pelletizing can be used to provide PAA particles fromcommercially available PAA resins, from mixtures comprising at least onethermoplastic and at least one antiviral or antimicrobial agent, andfrom mixtures thereof.

[0080] An advantage of sintering PAA particles formed by underwaterpelletizing is that the antiviral or antimicrobial agent(s) within theparticles thus formed are typically located near or on the surfaces ofthe particles. Without being limited by theory, this is believed to bedue to a phenomenon known as “surface segregation,” wherein antiviral orantimicrobial agents combined with molten thermoplastic(s) move to thesurface of the pellets during or after their formation. Materials formedby sintering such PAA particles will thus contain significant amounts ofantiviral or antimicrobial agents near or on the walls of the pores theycontain, since these pore walls are formed by the particles' surfaces.Consequently, this method can be used to provide materials whichcomprise antiviral or antimicrobial agents that are located where theywill most likely come into contact with viruses and/or microbes.

[0081] Because this process can be used to position antiviral orantimicrobial agents within porous materials at locations where they aremost effective, it can be used to avoid the inefficient, expensive, andpotentially hazardous overuse of antiviral or antimicrobial agentstypical of prior methods of producing viral- or microbe-resistantmaterials. For this reason, it may be preferable to limit theconcentration of antiviral or antimicrobial agent in the final productby forming PAA particles from a thermoplastic mixture made only in partfrom commercially available PAA resin. Alternatively, PAA particles canbe made solely by combining the necessary amount of antiviral orantimicrobial agent(s) with at least one conventional thermoplasticresin (i.e., a resin free of antiviral or antimicrobial agents).

[0082] As discussed above, if PAA particles are formed from a mixturecomprised of at least one thermoplastic and at least one antiviral orantimicrobial agent, it is important to select the thermoplastic(s) andantiviral or antimicrobial agent(s) to ensure that at least asubstantial portion of the antiviral or antimicrobial agent(s) will notdecompose during the underwater pelletizing or sintering processes. Thisis easily done, however, as the decomposition temperatures of individualantiviral or antimicrobial agents are well known or can readily bedetermined by conventional means. For example, an antiviral orantimicrobial agent can be heated to a specific temperature (e.g., thetemperature at which the thermoplastic melts) and then allowed to cool,after which its antiviral or antimicrobial activity can be measured.

[0083] The flexibility of the processes of this invention allow theproduction of porous materials using innumerable thermoplastics andantiviral or antimicrobial agents. This and other novel and unexpectedadvantages of the invention are further illustrated by the followingnon-limiting examples.

5. EXAMPLES 5.1. Example 1 Antimicrobial Coated Porous Media UsingPolyurethane as a Carrier

[0084] A polyurethane solution was prepared by mixing Pellethane®,supplied by Dow Chemical, with isopropanol as a solvent. Theconcentration of the polyurethane solution was adjusted around 5 weightpercent. After a transparent solution was formed, Triclosan® was addedinto the solution to obtain a concentration of 1 weight percent.

[0085] A porous polyethylene sheet having median pore size of 30 μm(part number X-4711, available from Porex Corporation, Fairburn, Ga.)was dipped into the prepared polyurethane solution for more than 1minute, after which the sheet was placed in a conventional or vacuumoven to allow the solvent evaporated completely. The dried product had athin layer of polyurethane without an obvious change of pore size andporosity.

5.2. Example 2 Antimicrobial Coated Porous Media Using PolyurethaneHydrogel as a Carrier

[0086] A polyurethane hydrogel was synthesized according to Example 1 ofU.S. patent application Ser. No. 09/375,383, filed Aug. 17, 1999, whichis incorporated herein by reference. The polyurethane solution wasprepared by mixing the hydrogel with methanol as a solvent. Theconcentration of the polyurethane solution was adjusted around 0.5weight percent. After a light yellowish solution was formed, Triclosan®was added into the solution to obtain a concentration of 1 weightpercent.

[0087] A similar porous polyethylene sheet as described in Example 1 wassubmerged into the solution for more than 1 minute, then the oven-dried.The dried part is coated with a thin layer of hydrogel, which whenexposed to water will swell to certain degree depending on thehydrophilicity of the polyurethane hydrogel. Advantageously, thisswelling was not sufficient to seal the pores of the polyethylenesubstrate.

5.3. Example 3 Antimicrobial Concentrates Incorporated Porous Media

[0088] Microban® 4010-100 concentrate in pellet form was cryogenicallyground in a WEDCO SE-12-L disk mill. The resulting microban powder,which had a median particle size of about 100 mesh (150 μm), was mixedwith an ultra high molecular weight polyethylene (GUR 2122 from Ticona)via dry blending in a 2:8 weight ratio. Since the concentrates powderand GUR powder have the similar particle size, the thorough mixing anduniform distribution of the concentrates was expected. After the mixturewas well blended, it was placed into a 0.25 inch flat mold. The mold washeated to 160° C. using electricity-heated plate for 4 minutes. Afterheating, the mold is cooled and the sintered porous sheet removed fromit.

5.4. Example 4 Porous Media Made from Underwater Pelletized Powder

[0089] Micropellets were made from H8EFA1 poly(ethylene vinyl acetate)(EVA; MFI=1.5) supplied by Equistar Chemicals, Houston, Tex., usingextruder equipped with a SLC-5 LPU underwater pelletizer available fromGala Industries, Inc., Winfield, W.V. Before extrusion, the EVA waspremixed with Microban® 4010-100 concentrate in a weight ratio of 8:2.The extruder used has three thermal zones set to 150° C., 165° C., and180° C. The underwater pelletizer was fit with a die with 0.020 inchholes drilled into it. The EVA was extruded through the die and into thecutter of the underwater pelletizer, which was rotating at 90-100 rpm toproduce a powder of 50 mesh (300 micron) diameter pellets.

[0090] The pellets were then dried and placed into a 0.25 inch flatmold. The mold was heated to 140° C. using electricity-heated plate for4 minutes. After heating, the mold was cooled and the sintered poroussheet removed from it.

5.5. Example 5 Carbon Black Incorporated Porous Media

[0091] As described in Example 3, Microban® concentrates werecryogenically ground to 200 mesh, then dried and mixed with carbon black(Cabot Corporation, Special Black Division; average particle size ofabout 30 μm) and ultra high molecular weight polyethylene (GUR 2122,available from Ticona Inc.) in a ratio of 5:10:85, respectively. Afterthe three types of powder were thoroughly mixed, the mixture was fedinto a 0.25 inch flat mold. The mold is heated to 140° C. usingelectricity-heated plate for 4 minutes. After heating, the mold wascooled and the sintered porous sheet removed from it.

[0092] The embodiments of the invention described above are intended tobe merely exemplary, and those skilled in the art will recognize, orwill be able to ascertain using no more than routine experimentation,numerous equivalents of the specific materials, procedures, and devicesdescribed herein. All such equivalents are considered to be within thescope of the invention and are encompassed by the appended claims.

What is claimed is:
 1. A porous thermoplastic material which comprises aporous thermoplastic substrate and an antiviral or antimicrobial agent.2. The porous thermoplastic material of claim I wherein the porousthermoplastic substrate is a porous thermoplastic selected from thegroup consisting of polyolefins, nylons, polycarbonates, poly(ethersulfones), and mixtures thereof.
 3. The porous thermoplastic material ofclaim 2 wherein the thermoplastic is a polyolefin selected from thegroup consisting of: ethylene vinyl acetate; ethylene methyl acrylate;polyethylenes; polypropylenes; ethylene-propylene rubbers;ethylene-propylenediene rubbers; poly(1-butene); polystyrene;poly(2-butene); poly(1-pentene); poly(2-pentene);poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;polychloroprene; poly(vinyl acetate); poly(vinylidene chloride); andmixtures and derivatives thereof.
 4. The porous thermoplastic materialof claim 3 wherein the polyolefin is a polyethylene.
 5. The porousthermoplastic material of claim 1 wherein the antiviral or antimicrobialagent is selected from the group consisting of: phenolic and chlorinatedphenolic compounds; resorcinol and its derivatives; bisphenoliccompounds; benzoic esters; halogenated carbanilides; polymericantimicrobial agents; thazolines; trichloromethylthioimides; naturalantimicrobial agents; metal salts; broad-spectrum antibiotics, andmixtures thereof.
 6. The porous thermoplastic material of claim 5wherein the antiviral or antimicrobial agent is selected from the groupconsisting of: 2,4,4′-trichloro-2′-hydroxydiphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.
 7. The porous thermoplastic material ofclaim 1 which further comprises a lubricant, colorant, or filler.
 8. Theporous thermoplastic material of claim 7 wherein the filler is selectedfrom the group consisting of: carbon black, cellulose fiber powder,siliceous fillers, polyethylene fibers and filaments, and mixturesthereof.
 9. A porous thermoplastic material which comprises: a sinteredporous polyethylene substrate; and an antiviral or antimicrobial agentselected from the group consisting of2,4,4′-trichloro-2′-hydroxy-diphenyl ether,3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea, poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride), silver ions, andsalts and mixtures thereof.
 10. A porous thermoplastic material whichcomprises: a sintered porous polyethylene core; and a coating layerdisposed over at least part of the porous polyethylene core; wherein thecoating layer comprises an antiviral or antimicrobial agent.
 11. Theporous thermoplastic material of claim 10 wherein the coating layerfurther comprises a thermoplastic or hydrogel material.
 12. The porousthermoplastic material of claim 11 wherein the thermoplastic or hydrogelmaterial is hydrophilic polyurethane.
 13. A particle comprising anantiviral or antimicrobial agent disposed within and/or on the surfaceof a thermoplastic core.
 14. The particle of claim 13 which has adiameter of from about 5 μm to about 1000 μm.
 15. The particle of claim14 wherein the thermoplastic core is made of a thermoplastic selectedfrom the group consisting of polyolefins, nylons, polycarbonates,poly(ether sulfones), and mixtures thereof; and the antiviral orantimicrobial agent is selected from the group consisting of:2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.
 16. A process for making a porousthermoplastic material which comprises sintering thermoplastic particlesto form a porous substrate and contacting the porous substrate with anantiviral or antimicrobial agent.
 17. The method of claim 16 wherein thethermoplastic particles are particles of polyolefins, nylons,polycarbonates, poly(ether sulfones), or mixtures thereof.
 18. Themethod of claim 16 wherein the antiviral or antimicrobial agent isselected from the group consisting of:2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.
 19. A product of the process of claim 16.20. A process for making a porous thermoplastic material which comprisessintering thermoplastic particles to form a porous substrate, andcontacting the porous substrate with a coating mixture which comprisesan antiviral or antimicrobial agent.
 21. The method of claim 20 whereinthe coating mixture further comprises a thermoplastic or hydrogelmaterial.
 22. The method of claim 21 wherein the thermoplastic orhydrogel material is hydrophilic polyurethane.
 23. The method of claim20 wherein the thermoplastic particles are particles of polyolefins,nylons, polycarbonates, poly(ether sulfones), or mixtures thereof. 24.The method of claim 20 wherein the antiviral or antimicrobial agent isselected from the group consisting of:2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.
 25. A product of the process of claim 20.26. A process for making a porous thermoplastic material which comprisessintering thermoplastic particles which comprise an antiviral orantimicrobial agent.
 27. The method of claim 26 wherein thethermoplastic particles are formed by underwater pelletizing a mixturecomprised of a thermoplastic and an antiviral or antimicrobial agent.28. The method of claim 26 wherein the thermoplastic particles areselected from the group consisting of particles of: polyolefins, nylons,polycarbonates, poly(ether sulfones), and mixtures thereof.
 29. Themethod of claim 28 wherein the polyolefin is polyethylene.
 30. Themethod of claim 26 wherein the antiviral or antimicrobial agent isselected from the group consisting of:2,4,4′-trichloro-2′-hydroxy-diphenyl ether;3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea; poly(iminoimidocarbonyliminoimidocarbonyl iminohexamethylene hydrochloride); silver ions; andsalts and mixtures thereof.
 31. A product of the process of claim 26.